If you are a U.S. Citizen please go to the link below at the U.S. State Department to determine if you need a visa to visit. Some countries like Turkey, China and Russia that normally require visas have waivers if you meet certain conditions.
The State Department’s Office of American Citizens Services and Crisis Management (ACS) administers the Consular Information Program, which informs the public of conditions abroad that may affect their safety and security. Country Specific Information, Travel Alerts, and Travel Warnings are vital pa…
As of this posting US citizens need an ETA for Australia. You will be denied boarding at the airport without having an ETA linked to your passport.
Australian Visa | Electronic Travel Authority
Apply for an Electronic Travel Authority to Australia
Starting in 2021, US citizens will also need an ETA for Europe.
Other helpful visa links:
Electronic Visa Application System
Republic of Turkey Electronic Visa Application System