if 2000 is enough to properly determine preferences within the US population as a whole, why don't we do away with the cost inefficient method of voting, and replace it with polling of 2000 US citizens?
Geez, there's a whole bunch of reasons why not.
Probably the most important is that we have this little thing called a Constitution. Now, granted, much of it has been effectively suspended by the current administration, but, nonetheless, we still have the right to vote. It's a sacred right in this country, and if anyone made any effort to curtail that on a nationwide basis as you suggest, most of us would start stockpiling weapons in Idaho.
Beyond that, there are practical reasons. Such a survey would be much, much easier to rig than a nationwide election. In addition, note that the margin of error is 3%. Quite a few elections are decided by percentages within that margin of error. Hence the results would be questionable. Also, deciding who is going to be running the country is a considerably more important question than what folks think of heathens, pagans and other undesirables. Given the seriousness of the question to be answered, polling just isn't an adequate method for answering the question.
I'm sure there are other reasons, but those are the ones I could come up with after about 5 minutes thought. The fact that those ideas never occurred to you suggests how long you took to really think about it before positing such an asinine question.
Those who would sacrifice an essential liberty for a temporary security will lose both, and deserve neither. -- Benjamin Franklin