Couple of thoughts. First, keep remembering that you each inherit about 50% from each parent, 25% from each grandparent, 12.5% from each gr grandparent and so on but NOT NECESSARILY THE SAME 12.5%. Think of it as the DNA lottery.
Second, it has been estimated that 53% of white Americans have colonial ancestry. That is a lot of descendants who have most all lived in the US for a couple of hundred years and were busy propagating all that time. This is as opposed to recent immigrants who may or may not have arrived with any family members and have had the opportunity to provide a much smaller pool of descendants to test.