The point is that it's more than just pyramids. It's food, glyphs, architectural design, way of life, etc.
There are so many close similarities, that I feel like we are missing something large.
Could you elaborate in more detail please?
Anyway, to explain the pyramids. Look
here. There are several reasons why they are refuted to be of the same culture.
Long story short:
The pyramids of Mexico and Egypt are separated by at least 2,000 years.
One of the largest differences between the Egyptian and Mesoamerican pyramids is the Egyptians use of only cut stone as both building material and decoration, which they quarried from sources, some of which were hundred of miles away, along the Nile. Though the degree to which the stones were polished or "finished" varied depending upon their location within the structure--stones being more finished varied directly with their proximity to the exterior surface of the pyramid--they were all finished to some degree. This method of using only cut stone enabled the Egyptians to construct a very sturdy central core that would withstand the centuries without modification. To them, this was an essential aspect of the design because according to their beliefs the pyramid was meant to house the body of the pharaoh, whom they considered a god, for eternity.
The pyramids of Mesoamerica, which are not even true pyramids, served an entirely different purpose, and as such, they were not built to withstand the ravages of time. Rather, these "step" or truncated pyramids rose in tiers, on the top of which a small temple was erected. Additionally, their central core was comprised primarily of large, irregular stones that they brought from the general area and piled. An exterior layer of cut stone served as a kind of retaining wall. To give the pyramids a finished look, their builders often added coats of stucco, sometimes colored blood red.
The people of the Old World possessed the true arch with its associated load-bearing keystone. Civilizations in the New World only possessed knowledge of the corbelled arch
Another key difference between the pyramids of Egypt and those of Mexico is the function that each had. The pyramids of Egypt were used as tombs for the pharaohs, and they were not meant to be entered once the dead pharaoh was placed safely inside. Those of Mexico, though sometimes housed the bodies of kings, were temples of public ceremony and ritual. Not only were they easily accessible via the staircases on their faces, they were also placed at the heart of cities. This contrasts sharply with the locations of the Great Pyramids, which were on the plains west of Memphis and the hidden nature of their recesses.
The most obvious difference between the pyramids of Mesoamerica and those of Giza is their physical appearance. The Pyramids of Cheops, Kephren, and Menkaure are all true pyramids. That is to say that their relative dimensions of equal and they rise in straight lines at a constant angle. Though there are exceptions to this among the earlier pyramids in Egypt this has more to do with the Egyptians learning the how to make a true pyramid than it has to do with them intentionally designing a truncated one, like the pyramids of Mesoamerica.
That wasn't so short though. My bad.