Semi automatic and fully automatic rifles have a great advantage over bolt action rifles in that they are a force multiplier - you can get more bullets downrange in the same amount of time which means you need fewer soldiers for covering fire actions, are more likely to hit a moving target and can engage multiple targets without having to remove the weapon from your shoulder.
However, the all the major powers, with the exception of the USA, went into WW2 with a bolt action rifle as their standard weapon, and the USA only adopted the M1 Garand in 1936. (The British had the Lee-Enfield, the Germans had the Karabiner 98K, the Soviets had the Mosin-Nagant and the Japanese had the Type 99.)
The French had developed and deployed several Automatic and semi-automatic rifles during and after WW1, yet they still chose to go with the bolt action MAS-36 in the lead up to WW2. The British army continued to use the Lee-Enfield right up until the mid 1950s!
So my question is: Why did none of the major powers, except for the USA, adopt semi automatic or fully automatic rifles as their standard military firearm?
Was it purely a matter of cost, or were there other factors at play such as tooling, supply, generals who didn't like change, etc?
Bonus question: Why didn't the US army adopt a lever action rile prior to WW1?
This question comes up regularly. More can always be said, and you can search and find a few postings, but there's a good answer and discussion here led by u/vonadler.
The question about lever-action rifles was answered pretty well here in a discussion led by u/Meesus . But the US did adopt a lever-action: for a few years after the Civil War, cavalry units were often equipped with the Spencer , until the Trapdoor Springfield was developed and the carbine version of that was issued.
There's a lot of factors involved, and the specifics tend to vary depending on which country you're looking at. In general, there was a combination of technological or mechanical limitations combining with poor timing of wars interrupting adoption. Keep in mind, armies had to experiment with a variety of different mechanisms and cartridges to find what worked, and they were often beset by unrealistic requirements that hindered development. Since you specifically call out France, I'm gonna focus on them, since they're a good case study.
Initial developments into semiautomatic service rifles began before WW1. France, with their early adoption of smokeless powder, was very quick to realize that semiautomatic rifles were the next step and had begun work on a semiautomatic service rifle as early as 1890. In their case, their earlier efforts to adopt a smokeless powder rifle as quickly as possible worked against them, as the 8mm Lebel cartridge was very poorly suited for a self-loading rifle. They took their time to get the system right, finally coming to a modern 7mm rimless cartridge and a long-recoil rifle known as the Meunier A6. Unfortunately for France, the rifle was selected for adoption in 1910 and it took another 3 years for the cartridge design to be finalized. Production finally began in Spring of 1914, but just a few months later the First World War broke out and the massive demand for rifles and ammunition meant that adopting a new rifle and new cartridge wasn't an option.
Although France would drop the Meunier, they'd continue their work on a semiautomatic rifle during WW1. However, due to wartime demands, they, like many other powers, would work to develop a "conversion" of their existing rifles. The result of these developments would be the RSC 1917/1918 - nominally a conversion of the Lebel 1886 rifle, but in reality an entirely new gun with a handful of superficial parts shared with the Lebel. However, it used the 8mm Lebel ammunition already in service, and the 1918 model would even use the same en-bloc clips used by the Berthier rifles. And for all of its flaws, it was arguably the first truly successful semiautomatic rifle, with a little under 90,000 of all models produced.
France had already recognized the limitations of its service rifles and cartridges long before WW1, so their efforts in the interwar period centered on a wholesale modernization of their infantry small arms starting with a new service cartridge and light machinegun. Again, cartridge developments slowed things down. The French had a new modern light machinegun chambering the new 7.5x57 cartridge in 1924, but they ran into issues with how easy it was to mix up the new cartridge with the superficially similar 8mm cartridges that had been received from Germany after the war. To fix the problem of mixing up ammo, the cartridge was shortened to 7.5x54mm and the FM 1924 machineguns updated to the 1924/29 model. Work had also begun on updating infantry rifles around the same time, but they took a unique approach to things. Not wanting to be caught in the middle of adoption like they were last time, the French had three phases of rifle updates - a modern semiautomatic rifle, a cheaper bolt-action reserve rifle, and a conversion for existing stockpiles to the 7.5mm cartridge. To save money and effort on tooling, the semiautomatic rifle and reserve rifle were to share as many parts as possible. Unfortunately, just like before, development dragged out. The MAS-36 - the bolt-action reserve rifle - was a fantastic execution of its concept to the point that I'd argue it was the best bolt-action service rifle ever designed, but that same year the M1 Garand was being adopted in America and the AVS-36 was (nominally) adopted in Russia. Even then, production was slow, and neither the MAS-36 nor conversions of older rifles were widespread enough in 1940 for the French Army to even be fully equipped with the 7.5mm cartrdige. The MAS-40 was even more drawn out, not entering production until just before the armistice.
Thus, although French factories were able to rapidly tool back up and begin production of the updated MAS-44 upon liberation, they only really managed to get their forces equipped with a semiautomatic rifle after the war.
Hopefully that gives you a decent idea of the kind of problems that prevented widespread adoption of semiautomatic rifles before WW2. If there's any specific countries you'd like me to elaborate on, let me know and I'll do my best to explain their situation.