I would use this xpath to find the above input:
browser.find_element_by_xpath(".//input[@value='Submit' and @type='submit']")
If there are multiple inputs with the same attributes, you may need to find by index as well.
UPDATE:
Since you are having trouble finding the element, and there are no iframes on the page, I would suggest using WebDriverWait in case there are any AJAX/JavaScript/Dynamic load events that are creating the input after the pageload is complete.
Import these into your script:
from selenium.webdriver.support.ui import WebDriverWait
from selenium.webdriver.support import expected_conditions as EC
from selenium.webdriver.common.by import By
Then try this:
wait = WebDriverWait(browser, 10)
wait.until(EC.element_to_be_clickable((By.XPATH, ".//input[@value='Submit' and @type='submit']"))).click()
As mentioned in your comment, you had to switch to a new tab. The way to do this in Selenium is:
#this will switch to the newest tab
browser.switch_to_window(browser.window_handles[-1])
Submit, rather thansubmit?