apart from india, are there any other countries where this deity is commonly worshipped?
Thailand, Cambodia, and among the Hindu classes of the Chams in Vietnam
Ganesha
 In Thailand, Cambodia, and among the Hindu classes of the Chams in Vietnam, Ganesha was mainly thought of as a remover of obstacles. 
who is the god of luck in hindu UNANSWERABLE in which scriptures is ganesha mentioned? Black Yajurveda why is this god worshipped? Ganesha is widely revered as the remover of obstacles, the patron of arts and sciences and the deva of intellect and wisdom. are there any festivals celebrated to honor this god? Yes, Ganesha Chaturthi when is it celebrated? Late August or early September what are the renowned temples in india dedicated to this god? Dhundiraj Temple in Varanasi, Uttar Pradesh; the Rockfort Ucchi Pillayar Temple at Tiruchirapalli in Tamil Nadu for how long was this god worshipped? Ganesha may have emerged as a deity as early as the 1st century BCE, but most certainly by the 4th and 5th centuries CE, during the Gupta period, though he inherited traits from Vedic and pre-Vedic precursors. are there any archaeological pieces of evidence to prove that this deity was worshipped in ancient times? Ganesha appears in China by the 6th century, states Brown, and his artistic images in temple setting as "remover of obstacles" in South Asia appear by about 400 CE.
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Ganesha [SEP] Beyond India and Hinduism
Statues of Ganesha are found throughout the region, often beside Shiva sanctuaries. The forms of Ganesha found in the Hindu art of Philippines, Java, Bali, and Borneo show specific regional influences. The spread of Hindu culture throughout Southeast Asia established Ganesha worship in modified forms in Burma, Cambodia, and Thailand. In Indochina, Hinduism and Buddhism were practised side by side, and mutual influences can be seen in the iconography of Ganesha in the region. In Thailand, Cambodia, and among the Hindu classes of the Chams in Vietnam, Ganesha was mainly thought of as a remover of obstacles.