Everyone is in a protected class because everyone has a nationality, immigration status, ethnicity, sex, sexuality, etc.
The EEOC investigates workplace discrimination, so if you suspect it, it would help to file a complaint with them. They can gather evidence to determine if discrimination took/takes placr and hold the employer accountable.
One of HRs jobs is to track % of people who are > 40. If you are a company of 1000 employees, and you are 25% of each age group 20+,30+,40+,50+ and you do a 100 person layoff, and 100% of them are 40+ - you will be sued and they will almost certainly win.
The EEOC investigates workplace discrimination, so if you suspect it, it would help to file a complaint with them. They can gather evidence to determine if discrimination took/takes placr and hold the employer accountable.