Doing it manually,
T = array2table(1:4,'VariableNames', {'America_1010', 'America_1008', 'America_1001', 'America_1808'}) % example table
numeric_string = regexp(string(T.Properties.VariableNames), '(\d*)', 'tokens'); % grab numeric part
numeric_value = cellfun(@(x)double(x{1}), numeric_string); % convert to double
[~, idx] = sort(numeric_value); % sort
T2 = T(:,idx) % reorder
But I'd recommend Stephen's natural sorting utilities as a way to skip sorting yourself:
