Because an American diet is in general more bland, it might take an aspiring cook more time to learn to create the quintessential Thai tastes with substitute ingredients. There is definitely a combination of flavors that defines Thai taste and that makes Thai food Thai. Every world cuisine uses more or less of each of these elements, but unique to Thailand is the harmonious play of each of these flavors together in a meal. Again it is the Thai taste that matters and not the individual ingredients. The history of Thai food is very creative.
Asian food uses what is at hand, varying with the seasons.
Thais have incorporated many foreign ingredients into their cuisine. For instance the chile pepper arrived only in the 16th century via South America. Peanuts are also a foreign adaptation. Even fish sauce they say has ancient Mediterranean roots. A cuisine is the taste preferences of a people-Thai, Vietnemese, American, etc.