Why didn't The Vikings/Norway just colonize the entirety of The Americas after they discovered it ?

EDIT: This post became much longer than expected, but I feel like the entire text is needed for a proper answer.

Well one answer is that Scandinavia was extremely sparsely populated with a low number of people. For example, in the year 1700, the Swedish Empire (Sweden, Finland, Estonia, Ingria, Livonia and their possessions in Northern Germany) had an estimated population of 2.5 million people, maybe slightly higher as the numbers in the Baltic and the German cities is difficult to gauge. Also, since the Viking expedition only reached Labrador and Newfoundland, cold and inhospitable places like Iceland and Greenland, it didn't exactly inspire colonization.

Then there's the lack of technology at the time. Though Longboats were remarkably seaworthy vessels for their time, one needs to bear in mind how primitive nautical technology and navigation actually were. Ships were built small, as the adhesives holding them together were weak and could not be employed in ungainly ships. At the time the lateen sail was not used in Europe, as it was an Arabic innovation originating much farther south in the Persian Gulf and the Mediterranean, and which was only latterly adopted by the Portuguese. Such sophisticated navigational instruments as astrolabes and compasses, were not in the possession of the Vikings.

So this lack of materiél naturally forced small and fragile ships to hug the coasts. There were three reasons for this general maritime timidity: to protect the ships from the harsh weather at open sea as much as possible, to be able to put ashore to escape pirates should those appear, and, perhaps most importantly, to replenish stocks of food and fresh water, which were in short order given the very tiny tonnages of the ships in question and their consequent lack of cargo space, further hampered by the presence of rowers occupying much space, who were necessary for propulsion.

We see, therefore, that a trans-Atlantic voyage in the style of Columbus was absolutely impossible in a Viking longboat, a Mediterranean galley, an Arab dhow, or any other vessel whose existence we know of prior to the Portuguese caravel.

The Portuguese Caravel was a veritable revolution in the history of seafaring. The caravel's size was much greater than anything that came before it, because it was built using enormous iron nails. The lateen was adopted, combined with the traditional square rigging in several masts, and this allowed the ship to be propelled and directed entirely by wind.

The new ship was additionally constructed with its deck high above the waterline, which its greater size made possible. This immensely improved seaworthiness and allowed the caravel, and the galleons that succeeded it, to hold the open sea indefinitely, and its much augmented cargo space allowed the more limited crew to survive for months on end at sea, whereas the crews of longboats or galleys would be lucky to avoid the necessity of restocking for a week.

Now indeed, from surviving models of longboats that have been found, we can presume that circa seventy feet was about average. Early caravel designs, including Columbus's Santa Maria, were somewhat shorter at only a little over sixty feet. But given superior construction, numerous sails, greater width of beam, and much greater draught, the Santa Maria could carry an estimated one-hundred and fifty metric tons while a longboat like the Gokstad Ship found in Norway could only carry twenty tons fully laden.

Now, the Vikings actually did reach North America, but it should be understood how this was possible.

Bearing in mind our knowledge that only by moving along the coast were ships able to safely travel, it becomes apparent that the Vikings darted relatively short distances across narrow waters. Plying the coasts of Germany and Holland they were able to reach the east coast of England and thence to Scotland and the Orkneys. A more direct route lay by jumping across the Shetlands to the Orkneys, northern Scotland, and Ireland.

These islands were long held by the Scandinavians and were their entry point into Britain once the continental route to the south became too dangerous.

It is also known that the Vikings used somewhat unorthodox navigational techniques, such as famously employing ravens to help them discover land. Ravens would be brought on deck, and released at intervals. They would never land in the water, of course, so if they spotted land they'd fly towards it, leading the Vikings to it. If they did not see land, they'd simply fly for awhile then return to the ship.

Finally, reaching Labrador and Newfoundland, the Vikings found little in the way of use to them. In order to continue they both had to establish bases of supply and repair, meaning actual communes permanently living in these stations, which took years.

The same is true of Henry the Navigator, who began the Portuguese explorations in 1419, yet the Portuguese did not reach the Gold Coast at Elmina until 1471, which was nearly two-thousand four hundred miles away from Lisbon.

Anyway, this gradual leap-frogging is distinctly characteristic of pre-Columbian nautical ability. It greatly resembles nothing so much as the practices in the Mediterranean, what the Italians called "sailing by the islands".

For example from Sicily to Crete to Cyprus, or from the Balearics to Corsica or Sardinia. Never did Mediterranean vessels sail from one end to the other without stopping, and they avoided the open wastes as far as possible.

The difference though is that the Mediterranean was well populated and possessed of abundant resources at all stages without the mariners having to found miserable colonies in unwelcome climates from scratch.

Accordingly, only very small numbers of people could actually sail, and the leap from Greenland to Baffin Island and Labrador, the latter what the Vikings called Vinland, was logistically very taxing.

The coast of Labrador provided precious little of either. The coast of Labrador, even today, is bleak and rocky. The Vikings attempted to establish a base here, but it ultimately proved unsustainable, and they were thus unable to push any further.

We know also that the climate shifted on them, became colder, and this is generally assumed to be the cause of their extinction in the far north. Not only the settlements of Labrador, but of Greenland too, were abandoned.

So: why didn't they colonize "central" Northern America?

They didn't know there was such wast territory south of Labrador.
Even if they did, they did not know whether they would be able to sustain themselves there, and since they could not replenish at Labrador, they could only, at most, sail extremely short distances before being forced to turn back due to lack of supplies. Even worse, establishing a colony and making it work so it could sustain colonizers and repair ships would take years, years of being unable to survive.