Wordpress changing site URL with WWW give problems

In wordpress admin panel, settings/general, I changed the "site URL" from site.com to www.example.com

so now I have:

WordPress Address (URL) : http://example.com

Site Address (URL): http://www.example.com

(Wordpress in installed on root)

But I have problems because it's clear that paths are not correctly read from code: site is visible but but icons fonts is not visible admin have problems and so on...

I asked to disable openbase_dir option to my provider Nothing changed I tryed to add

RewriteCond %{HTTP_HOST} ^(www.)?example.com$

but not all was fixed...

Anyone could help me please? thank you !!!

.HTACCESS

# BEGIN WordPress
<IfModule mod_rewrite.c>
RewriteEngine On
RewriteBase /
RewriteRule ^index\.php$ - [L]
RewriteCond %{REQUEST_FILENAME} !-f
RewriteCond %{REQUEST_FILENAME} !-d
RewriteRule . /index.php [L]
</IfModule>

# END WordPress

RewriteCond %{HTTP_HOST} ^(www.)?example.com$