It is unclear from your question if you were refused a visa (from a consulate) or if you were refused entry (at the border) and from which country you received this refusal. This may be relevant, but probably not.
If the refusal is 15 years old and from any EU country, it is likely not on record anymore. All EU countries must follow relatively strict data protection regulations and are simply not allowed to keep such records for a very long time. Currently, records of Schengen visa refusals are only kept for five years in the central VIS register and then deleted.
In any case, the current common border and visa code for the Schengen area clearly states that each visa application or entry attempt shall be independently assessed. A previous visa or entry refusal shall not count against you if you try to reapply for a visa or seek entry again and your circumstances have actually improved. In case of visa refusals which are still on file, you must of course expect heightened scrutiny in the examination of your visa application and perhaps a more thorough verification of your current story to detect 'creative fixing', but if your circumstances really have improved and this can be clearly documented, an old refusal will not mean that a new attempt will fail.
If you arrive in Amsterdam with a low risk passport, as the US passport is, and don't look obviously conspicuous in any way, I would deem the chances that you are questioned by the immigration officer at all to be extremely low. You will probably be 'stamped in' without any conversation at all.