How many reactionaries are there in America?

There are several points to consider here.

The definition of reactionary will differ according to your point of view.

America is a huge continent. The government or people of Bolivia may consider a group reactionary whilst the government and people of Canada may consider that group acceptable.

Many so called reactionary groups are secretive and do not publish their numbers.

In short the true number cannot be known and would be different for each according to political, religious and other affiliations.