I'm not aware of Germany every having any hope of inducing Japan to declare war on the US during WW1, certainly not by 1917, given that Japan was allied to Britain from 1902 through 1923. Japan and Britain's relationship had been renewed in 1911 and Japan honored the alliance by joining WW1 on the Entente side promptly in August 1914: Japan commenced operations against the German-controlled Chinese city of Tsingtao (one of several port cities that China had been induced to lease to European powers as trading ports and naval bases, similar to the British lease of Hong Kong and the Russian lease of Port Arthur) on August 27, 1914, landed troops to besiege the city in early September, and captured the city in November of the same year. Japan also captured several German island colonies in the Pacific (several of which featured prominently in the Pacific Theater of WW2): the Marshall Islands, the Carolines, and the Mariana Islands. Japan also sent a number of cruisers and destroyers to reinforce Entente convoy escort and sub-hunting missions in the Mediterranean elsewhere starting in 1917.

Germany did try to negotiate a separate peace with Japan during the middle years of the war, which might be what you're thinking of. As far as I know, these talks went nowhere. Japan did have a significant strategic rivalry with the US at the time, mainly focusing on conflicting policies towards China (Japan had aspirations of colonial conquest against China, while the US had major trading interests in China and favored an "Open Door" policy where China remained independent and free to trade with all major western powers), so Japan would have had at least a little motivation to side with Germany against the US if not for Japan's alliance with Britain. Relations between the US and Japan would of course continue to sour after the war, contributing to the decision not to renew the Anglo-Japanese alliance in the early 1920s (as Britain decided to prioritize friendly relations with the US over continued alliance with Japan) and of course to Japan aligning with Nazi Germany in the 1930s and declaring war on the US and Britain in December 1941.

Germany did try to negotiate an alliance with Mexico against the US in 1917, which Mexico briefly considered and rejected because Mexico (being much poorer and militarily weaker than the US and still dealing with lingering internal guerrilla rebels follow a major civil war) was in no fit state to fight the US and because they rightly doubted the ability of Germany to support and reinforce the hypothetical Mexican war effort. I've previously written about this in more detail here, along with details about then-recent Mexican grievances against the US that might have suggested to German diplomats that such a proposal would be welcome.
But let us suppose for the sake of argument that German had somehow succeeded in negotiating a separate peace with Japan in 1915 or 1916 and then somehow induced both Japan and Mexico to declare war on the United States upon American entry into the war against Germany in or around April 1917.

The US Navy was substantially but not overwhelmingly stronger than Japan's in mid-1917. Japan had six Dreadnought battleships in commission, plus four battlecruisers and ten Pre-dreadnoughts (older models of battleship which were significantly less combat-effective than Dreadnoughts, being generally slower and having a mixed main battery instead of the uniform armament of 12-15 inch guns mounted on Dreadnought-style designs). The US had 14 Dreadnoughts and 23 Pre-dreadnoughts. The US did have two oceans to worry about and traditionally distributed peacetime deployments between the Atlantic and Pacific, but Japan would have been the main threat to the US with the German fleet bottled up in the North Sea following the Battle of Jutland. Some of the American dreadnoughts (the two South Carolina class battleships in particular) were considerably smaller and more lightly-armed than any Japanese dreadnoughts, but countervailing that the US Navy's dreadnoughts included six "superdreadnoughts" with 14-inch main guns to the Imperial Japanese Navy's two such ships. How conflict between the two fleets would have played out in a real war is an unanswerable counterfactual, but the US would have had a significant advantage to begin with which would likely grow larger as the war dragged on due to the far larger American industrial base, but it's not completely implausible that bad strategic and tactical decisions might have let the IJN win some key battles and whittle down the USN enough to achieve temporary naval superiority in the Pacific until some combination of British reinforcements and new American construction tipped the scales back the other way.

As for an actual invasion, that's a very tall order even with regional naval superiority (and impossible without it), bordering on implausible. To understand why, we'd want to consider what makes naval invasions difficult and what's necessary to . The hardest invasions to pull off are execute them successfully in the face of determined opposition.

The first big set of problems is actually getting the troops to the shore along with their weapons and enough food, ammunition, etc to keep them alive and combat effective long enough to secure a beachhead. For this, you need some kind of transport to carry the soldiers and their supplies and equipment from a friendly port (big enough and well-supplied enough to stage the invasion force and its baggage train, embark them, and top off the fuel supplies of the invasion fleet) to the invasion beach, and you also need warships with enough range to accompany the fleet and ideally make it back to a friendly port. Japan would have been hard-pressed for the warships: the newest battleships (the Fusō class) had more than enough range for a round-trip from the Japanese Home Islands to Hawaii and from Hawaii to the West Coast of the American mainland, and nearly enough range for a round trip directly from the Home Islands to the West Coast. But Japan only had two Fusōs (along with four Kongō-class battlecruisers that were similarly long-ranged), and their older dreadnought had much shorter legs and would have only been capable of a one-way trip even as far as Hawaii. Japan's lighter warships, most notably destroyers, would also have needed to refuel on their way to escort an invasion fleet. Refueling at sea is possible, but that further increases the logistical demands on the invasion effort.

The troop transports and sealift for associated supplies and equipment is also an extremely tall order. Per Tadaaki Shindo's "A Brief History of the Japanese Merchant Marine Fleet", Japan had a total available merchant ship capacity of 1.58 million tons in 1914 and 2.31 million tons in 1918. By comparison, Japan's real-life naval operations in 1941 and early 1942 required nearly 4 million tons of shipping to support according to Mark Parillio's "The Japanese Merchant Marine in World War II" (1.5 million tons for troop landings, mostly in the Philippines and Malaya, 600k for other army supply needs, and 1.7 million for keeping the navy supplied in forward bases), so even if Japan completely stripped their civilian economy of merchant shipping, they'd have well short of the shipping capacity they'd need to conduct a large-scale invasion.

Next is the problem of getting troops ashore and securing a beachhead. This is a problem that was vastly underestimated in World War I, with operational planners imagining that they could simply approach the shore with troop transports or towed barges and have the soldiers and marines climb down over the side and wade ashore. This turns out to work out extremely poorly in the face of any sort of prepared defense, such as during the opening phase of the Gallipoli campaign. To have good odds of taking a beach, you need at least one of 1) overwhelming superiority of numbers and firepower, 2) purpose-built landing craft, or 3) total operational surprise so you can take the beach before the defenders realize what's happening. Then you need to worry about stuff like capturing a port intact, breaking out from the beach, and actually defeating the main enemy force and taking your ultimate objectives.

Getting ashore and doing something worthwhile once you're there is somewhat easier in a scenario where both Mexico and Japan are at war with the US, since Japan would then have the option of steaming their invasion fleet into a friendly port on Mexico's West Coast and unloading directly onto the docks, then taking Mexican trains and roads to battle on the front lines. Even so, Japan and Mexico face huge challenges: the aforementioned problems with moving troops, equipment, and supplies across the Pacific in the necessary quantities and escorting the transports against interception attempts by the US Navy, the relatively undeveloped infrastructure of Northern Mexico in 1917, the Villista rebels operating in the border region (who were at war with both the US and the official Mexican government), and of course the US Army itself. The US had a very small peacetime military in 1917, but was able to mobilize a very large army in a matter of months. The US Army would have been fighting close to home (also close to Mexico, but Japan's an entire ocean away), and would have had a larger population and far larger industrial base than Japan and Mexico combined.