Does Swanson reveal country of origin on its ingredients. If not then they are just blowing smoke up the consumer’s asses.
Many herbs in particular have to come from overseas because they’re only grown in certain areas. They guarantee product potency and purity through 3rd party independent labs.
Can’t do much more than that. Ultimately there’s no guarantee anything you buy is exactly as stated. The only thing you can do is rely upon independent 3rd party auditors.
I have found their products to be excellent resulting in dramatic health improvement for me personally.