Actually there are Barclays in the USA, so your assumptions are invalid.. the following is from their web site:
http://group.barclays.com/about-barclays/about-us/usa - just click on the "contact us" tab
"You can use the following details to contact our investment bank in the US:
Atlanta
3344 Peachtree Road, Suite 950, Atlanta, GA 30326, USA
Telephone: + 1 404 262 4800
Boston
125 High Street,
Boston, MA 02110, USA
Telephone: +1 617 330 5800
Chicago
190 South La Salle Street, Chicago, IL 60603, USA
Telephone: + 1 312 609 7200
Dallas
200 Crescent Court
Suite 400, Dallas, TX 75201, USA
Telephone: +1 214 720 9470
Houston
Fullbright Tower, 1301 McKinney Street, Suite 400, Houston, TX 77010, USA
Telephone: +1 713 401 6800
Fax: +1 713 401 6752
Los Angeles
10250 Constellation Boulevard, 24th Floor, Los Angeles, CA 90067, USA
Telephone: +1 310 481 2600
Menlo Park
155 Linfield Drive, Menlo Park, CA 94025, USA
Telephone: +1 650 289 6000
Fax: +1 650 321 2207
Miami
1111 Brickell Avenue, 12th floor, Miami, FL 33131, USA
Telephone: +1 305 789 8700
New York
745 Seventh Avenue, New York, NY 10019, USA
Telephone: +1 212 526 7000
Portland
1001 SW Fifth Avenue, Suite 1100, Portland, OR 97204, USA
Telephone: +1 503 535 8062
Fax: +1 503 535 0714
San Francisco
555 California Street, 30th floor, San Francisco, CA 94104, USA
Telephone: +1 415 263 3300
Santa Monica
1620 26th Street, Water Garden Building, Santa Monica, CA
90404, USA
Telephone: + 310 907 0510
Seattle
701 Fifth Avenue,
Suite 7101,
Seattle, WA 98104, USA
Telephone: +1 206 344 5870
Fax: +1 206 233 2817
Washington DC
2001 K Street NW, Washington DC 20005, USA
Telephone: + 1 202 452 4700
For press enquiries
Telephone: +1 212 412 7545
Email: corporatecommunicationsamericas@barclays.com